title: Molecular analysis of the sex chromosomes of the platyfish Xiphophorus maculatus: Towards the identification of a new type of master sexual regulator in vertebrates.
abstract: In contrast to mammals and birds, fish display an amazing diversity of genetic sex determination systems, with frequent changes during evolution possibly associated with the emergence of new sex chromosomes and sex-determining genes. To better understand the molecular and evolutionary mechanisms driving this diversity, several fish models are studied in parallel. Besides the medaka (Oryzias latipes Temminck and Schlegel, 1846) for which the master sex-determination gene has been identified, one of the most advanced models for studying sex determination is the Southern platyfish (Xiphophorus maculatus, Günther 1966). Xiphophorus maculatus belongs to the Poeciliids, a family of live-bearing freshwater fish, including platyfish, swordtails and guppies that perfectly illustrates the diversity of genetic sex-determination mechanisms observed in teleosts. For X. maculatus, bacterial artificial chromosome contigs covering the sex-determination region of the X and Y sex chromosomes have been constructed. Initial molecular analysis demonstrated that the sex-determination region is very unstable and frequently undergoes duplications, deletions, inversions and other rearrangements. Eleven gene candidates linked to the master sex-determining gene have been identified, some of them corresponding to pseudogenes. All putative genes are present on both the X and the Y chromosomes, suggesting a poor degree of differentiation and a young evolutionary age for platyfish sex chromosomes. When compared with other fish and tetrapod genomes, syntenies were detected only with autosomes. This observation supports an independent origin of sex chromosomes, not only in different vertebrate lineages but also between different fish species.
authors.affiliation: Institute of Functional Genomics, Ecole Normale Supérieure de Lyon / Université de Lyon, Lyon, France.
authors.forename: Astrid
authors.initials: A
authors.lastname: Böhne
authors.forename: Christina
authors.initials: C
authors.lastname: Schultheis
authors.forename: Delphine
authors.initials: D
authors.lastname: Galiana-Arnoux
authors.forename: Alexander
authors.initials: A
authors.lastname: Froschauer
authors.forename: Qingchun
authors.initials: Q
authors.lastname: Zhou
authors.forename: Cornelia
authors.initials: C
authors.lastname: Schmidt
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Selz
authors.forename: Catherine
authors.initials: C
authors.lastname: Ozouf-Costaz
authors.forename: Agnès
authors.initials: A
authors.lastname: Dettai
authors.forename: Béatrice
authors.initials: B
authors.lastname: Segurens
authors.forename: Arnaud
authors.initials: A
authors.lastname: Couloux
authors.forename: Sylvie
authors.initials: S
authors.lastname: Bernard-Samain
authors.forename: Valérie
authors.initials: V
authors.lastname: Barbe
authors.forename: Stefan
authors.initials: S
authors.lastname: Chilmonczyk
authors.forename: Frédéric
authors.initials: F
authors.lastname: Brunet
authors.forename: Amandine
authors.initials: A
authors.lastname: Darras
authors.forename: Marta
authors.initials: M
authors.lastname: Tomaszkiewicz
authors.forename: Marie
authors.initials: M
authors.lastname: Semon
authors.forename: Manfred
authors.initials: M
authors.lastname: Schartl
authors.forename: Jean-Nicolas
authors.initials: JN
authors.lastname: Volff
mesh_terms: D000818:Animals; D022202:Chromosomes, Artificial, Bacterial; D003532:Cyprinodontiformes / Q000235:genetics*; D019143:Evolution, Molecular; D012730:Sex Chromosomes / Q000235:genetics*; D019849:Sex Determination Processes / Q000235:genetics*; D026801:Synteny / Q000235:genetics